ETANERCEPT

Fetal Risk Summary

Etanercept is a dimeric fusion protein, produced by recombinant DNA technology (Chinese hamster ovary mammalian cell expression system), consisting of the extracellular ligand-binding portion of the human kilodalton (p75) tumor necrosis factor receptor (TNFR) linked to the Fc portion of human IgG1. The protein binds specifically to tumor necrosis factor, a cytokine involved in inflammatory and immune responses, to block its interaction with cell surface TNFRs (1,2). Etanercept is indicated for reducing the signs and symptoms and delaying structural damage in moderate to severe rheumatoid arthritis, including juvenile arthritis. The drug is administered by SC injection.

Reproduction studies in rats and rabbits at doses 60 to 100 times the human dose revealed no fetal harm (1,2). Animal fertility and carcinogenic studies have not been conducted with etanercept, but it was not mutagenic in in vitro and in vivo tests.

No reports describing the use of etanercept during human pregnancy have been located. One review of rheumatic disease therapy recommended that pregnancy should be excluded before etanercept was administered to women of childbearing age (3). The reviewer also recommended that effective contraception be used during treatment. Another review speculated that etanercept could disrupt pregnancy because of its anticytokine activity (4).

Breast Feeding Summary

No reports describing the use of etanercept during human lactation have been located. The effects of exposure to this protein on a nursing infant are unknown (4). Because etanercept is a protein, it most likely would be digested in the infants' stomach and not absorbed systemically.

References

1. Product information. Enbrel. Immunex, 2001.
2. Product information. Enbrel. Wyeth-Ayerst Pharmaceuticals, 2001.
3. Janssen NM, Genta MS. The effects of immunosuppressive and antiinflammatory medications on fertility, pregnancy, and lactation. Arch Intern Med 2000;160:610–9.
4. Jarvis B, Faulds D. Etanercept. A review of its use in rheumatoid arthritis. Drugs 1999;57:945–66.